[darcs-users] how to redistribute darcs+Eclipse (was: Darcs API?)

David Roundy droundy at darcs.net
Fri Jun 3 12:21:39 UTC 2005


On Thu, Jun 02, 2005 at 05:09:32PM -0300, zooko at zooko.com wrote:
> 
> Dear David Roundy and all other darcs copyright holders:
> 
> Please act now, before the situation gets more complicated or staler.
> Please publically state that you allow GPL'ed darcs source code to be
> mixed with IBM Common Public License code.  Remember, this is not going
> to allow people to use darcs in a proprietary project.  The only thing it
> is going to do is to allow people in the future to mix darcs code with
> CPL'ed projects such as Eclipse.

I've read over the CPL (http://www.eclipse.org/legal/cpl-v10.html), and
have no objection to dual-licensing darcs.  The CPL is indeed quite similar
in spirit to the GPL.  I don't see any loopholes, and I suspect the IBM
lawyers put some thought into making it enforceable.

On the other hand, this isn't a high priority for me.

And item #19 of the FAQ:

  If I write a module to add to a Program licensed under the CPL and
  distribute the object code of the module along with the rest of the
  Program, must I make the source code to my module available in accordance
  with the terms of the CPL?  No, as long as the module is not a derivative
  work of the Program.

suggests that there is a loophole, since one could create a proprietary
module that gives "extra" features and distribute this together with the
CPLed program, as long as the module is not a derivative work.  I guess
this is related to the fact that the CPL is shorter than the GPL and is
less specific about what constitutes legal distribution.  In any case, it
does seem like a loophole that effectively allows proprietary derivatives
to be created--with the restriction being that they'd have to isolate the
proprietary code in a module, and somehow keep it from becoming a
"derivative work" (whatever that means).

I'm also not really clear as to why this is an important issue.  What sort
of eclipse interface would you imagine that would need to be more closely
integrated with darcs than the current interface allows? Also, since the
CPL (according to FAQ #19 quoted above) allows non-CPL modules, why
couldn't a hypothetical darcs eclipse plugin be licensed under the GPL?

In summary, if you (or anyone else) wanted to contact all the darcs
contributors to get agreement to dual-license darcs under both GPL and CPL,
I'd agree.  But it's not something that greatly interests me, and I'm not
going to go to the trouble myself.

Also note that we can have separate license headers on each file, so one
could go through the history of each file and update their licenses
separately, although you'd have to be careful about code that might have
been copied from one file to another.  A hypothetical eclipse plugin
probably wouldn't use most of the code in darcs, and the number of
contributors to the Patch* modules, for example, is much less than the
number of contributors to the interface portions of the code.  One could
also reduce the effort by dual licensing only the code portion (not the
literate documentation) of the files.
-- 
David Roundy
http://www.darcs.net




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